1. Field of the Invention
The present invention relates to a maintenance mechanism for cleaning and protecting a print head of a printing machine of the ink jet printing system wherein printing is performed by jetting ink droplets onto a receiving medium.
2. Description of the Related Art
Ink-jet printing machines generally have three modes of operations which include a printing operation for printing on a receiving medium, a capping operation for protecting a print head and preventing nozzles from drying, and a wiping operation for cleaning by wiping surfaces of the nozzles of the print head. FIGS. 11A to 11C illustrate an example of the conventional print head maintenance mechanism, while an example of such an arrangement of the maintenance mechanism is disclosed in Japanese Unexamined Patent Publication JP-A 2000-233517 (2000).
FIG. 11A shows a state where a nozzle portion disposed at a respective bottom of a first and a second print head 3, 4 (lower portions as seen in the figure) is sealed by a respective cap 7a, 7b. The first and second print heads 3, 4 are mounted to a carriage 2 adapted to reciprocate along a primary scanning direction as carried on a carriage shaft 5 extended transversely of a main frame 1. At this time, a slide case 6 provided with the caps 7a, 7b is positioned at a left end of the main frame 1 as operatively connected with the carriage 2 as shown in FIG. 11A, the left end of the main frame 1 defining one end of a primary scanning movement. That is, the slide case 6 is placed at an uppermost position (a top dead center) by means of a function of sliding projections C slidably engaged with slanted cam grooves B formed in a base portion 9 of the printing machine, so that the print heads 3, 4 are sealed by the caps 7a, 7b. 
FIG. 11B shows a state where the wiping operation is being carried out for cleaning by wiping the nozzle surfaces at the print heads 3, 4. At this time, the slide case 6 has the sliding projections C thereof fixed to a respective intermediate position of the cam grooves B by means of a lock mechanism (not shown), so that the caps 7a, 7b are spaced away from the nozzle surfaces at the print heads 3, 4. The carriage 2 passing over wipers 8 permits the wipers 8 to wipe and clean the nozzle surfaces at the print heads 3, 4.
FIG. 11C shows a state where the printing operation is being carried out. At this time, the carriage 2 is further moved rightward from the position shown in FIG. 11B or moved toward the other end of the primary scanning movement relative to the main frame 1 by a distance L1 from the one end of the primary scanning movement, thus entering a printing region for performing the printing operation. In this state, the slide case 6 is released from the locked state while the sliding projections C rest at a respective right end of the cam grooves B in conjunction with the movement to the other end of the primary scanning movement relative to the main frame 1. The slide case 6 is at a lowermost position (a bottom dead center) or at such a height as to bring the wipers 8 and caps 7a, 7b out of interference with the operating print heads 3, 4, so that a normal printing operation is allowed.
According to the conventional example mentioned above, a main body of the printing machine requires a further widthwise (the primary scanning direction) increase of space, such that the slide case 6 may be allowed to move a distance L2 from the one end of the primary scanning movement relative to the main frame 1 thereby permitting a sequence of oblique sliding movements of the maintenance mechanism. Specifically, the space represented by L2 in the figure is required to permit the slide case 6 to move up and down or to permit the sliding projections C in loose fit with the cam grooves B to slidably move in conjunction with the movement of the carriage 2. This requires the further widthwise increase of space of the printing machine, which results in an increased widthwise dimension of the machine.
As a solution to this problem, for example, Japanese Unexamined Patent Publication JP-A 2000-203042 (2000) discloses an arrangement wherein a maintenance station is disposed within the printing region. In this case, a motor conventionally provided for driving a sheet feed roller or feed roller is utilized for driving the maintenance station. However, such an arrangement encounters a complicated structure of a drive force transmission mechanism and an increased number of components thereof. Consequently, a driving system has a complicated structure of a complicated control, which results in increased costs.
On the other hand, U.S. Pat. No. 5,455,609 discloses an arrangement employing the following drive force transmission mechanism for vertically moving the maintenance station. The transmission mechanism is arranged such that a worm gear mounted to an output shaft of a motor is meshed with a wheel gear, which is meshed with a rack. Unfortunately, this arrangement also suffers the complicated structure of the driving system.